SINCLAIR : MARSUPIALIA OF THE SANTA CRUZ BEDS. 
421 
The mandible is of the same depth as in Ccenolestes , with the lower 
border approximately horizontal. Two conspicuous mental foramina are 
present, situated respectively beneath the posterior premolar and the 
anterior portion of the second molar. 
Halmarhiphus may be distinguished from Ccenolestes by the sharper 
separation of the molar cusps, which in the latter are tending toward the 
crescentic pattern of the Palaeothentinae. The molar crowns are less 
quadrangular in outline and the metaconid on Mr is less reduced than in 
Ccenolestes. More important differences would probably appear in the 
upper dentition. Garzonia is readily separated from Halmarhiphus and 
Ccenolestes by the single-rooted condition of Mi. 
Halmarhiphus nanus Ameghino. 
(Plate LXIII, Figs. 9, 9 a ; Text Fig. 7.) 
Halmarhiphus nanus Amegh. ; Revista Argent., T. I, p. 308, 1891; 
Enum. Syn., p. 101, 1894; Bol. Ac. Cord., p. 357, 1894; Segundo 
Censo, etc., p. 187, 1898. 
The right half of a lower jaw of this little animal (No. 9593 American 
Museum of Natural History) was collected by Mr. Barnum Brown on the 
Rio Gallegos. Until a larger amount of material has been secured, the 
generic and specific characters cannot be separately stated. The princi- 
pal measurements are as follows : 
Measurements. 
Length of lower dental series from posterior border of alveolus of I T to M T 
inclusive ...... 
Length of antemolar series exclusive of I T 
“ molar series ....... 
Width of base of median incisor 
Depth “ “ “ “ “ 
Median premolar, antero-posterior diameter .... 
“ “ transverse “ 
Posterior “ antero-posterior “ 
“ “ transverse u 
My, antero-posterior diameter ..... 
“ transverse "... 
Mg, antero-posterior "... 
“ transverse “ 
Mg, antero-posterior diameter ..... 
“ transverse “ 
.008 
.003 
.005 
.0008 
.001 
.0012 
.0005 
.001 
.0006 
.0014 
.001 
.0016 
.0012 
.0014 
.001 
